Pumpkin is a highly nutritious plant, rich in valuable nutrients that benefit human health. Due to the high perishability of this fruit, the production of pumpkin juice is a practical way to use it effectively. Recently, fermented vegetable juices have been used as a dairy alternative due to their nutritional and potential probiotic properties. This study investigated the fermentation of pumpkin juice using different strains of lactic acid bacteria (LAB), with and without heat treatment. The effects of fermentation on microbial growth, pH, acidity, extract, sugars, carotenoids, polyphenols, and antioxidant properties were analyzed. The heat-treatment process did not greatly impact the dry matter content, pH, acidity, extract, or sugar content. However, it led to a reduction in carotenoid and polyphenol levels. During fermentation, there was a consistent decrease in pH and an increase in total acidity, with no noticeable differences between bacterial strains regarding their influence on these parameters. The study revealed that there were no distinctions between LAB strains in their effects on pH, acidity, and carotenoid content in fermented pumpkin juice. Nonetheless, both L. sakei and L. plantarum proved to be effective in the fermentation process, with L. sakei demonstrating greater adaptability. The expected pH, acidity, and sugar content changes were consistently observed throughout the fermentation process. Overall, results confirm the efficacy of the used Lactobacillus strains in fermenting pumpkin juice and highlight the potential impact of heat treatment on the nutritional composition of the juice. The purpose of thermal processing of pumpkin juice, which is conducted with lactic acid fermentation, is crucial for the food industry. It extends the product’s shelf life, improves its nutritional and taste profiles, and guarantees its microbiological safety.

This study evaluated the energy-dependent effects of pulsed electric field (PEF) treatment on the physicochemical properties, bioactive compounds, antioxidant activity, and microstructure of red bell pepper (Capsicum annuum L.). Red bell pepper tissue was treated at specific energy inputs ranging from 1 to 10 kJ/kg and compared with a fresh (untreated sample). The cell disintegration index (CDI) increased progressively with PEF energy, confirming enhanced membrane permeabilization and structural disruption. Structural analyses (SEM and micro-CT) confirmed the formation of pores and interconnected channels, particularly at moderate and high energies. PEF treatment caused a decrease in total polyphenols and flavonoids, whereas vitamin C and total carotenoid contents increased at intermediate energies. Antioxidant activity (ABTS, DPPH, FRAP) declined overall but remained at comparable levels for mild PEF exposure. A significant reduction in firmness was observed (from 17% to 27% compared with the untreated control), and color changes were dependent on the energy input, while microstructural degradation intensified as the energy level approached 10 kJ/kg. PEF treatment improved microbial stability, resulting in a measurable reduction in total viable counts and yeast and mold counts, particularly at higher energy inputs. FTIR, TGA, and NMR data confirmed molecular alterations without degradation of major components. Multivariate analysis (dendrogram, PCA) distinguished four characteristic response groups: fresh, low-energy (1–2 kJ/kg), moderate-energy (4–5 kJ/kg), and high-energy (10 kJ/kg). PEF treatment selectively modified red bell pepper tissue, enhancing permeabilization and carotenoid/vitamin C release while preserving visual quality at mild–moderate energies. These results demonstrate the potential of PEF as a nonthermal technique for tailoring the structural and functional properties of plant-based products.

Lactic acid fermentation has emerged as a promising strategy to enhance the functional and health-promoting qualities of plant-based foods. This study evaluates the impact of lactic acid fermentation on the antioxidant capacity, microbial viability, and chemical stability of freeze-dried peaches, aiming to develop a functional food with probiotic potential. Two bacterial strains—Fructilactobacillus fructivorans (P_FF) and Lactiplantibacillus plantarum (P_LP)—were used to assess strain-dependent effects on microbial and bioactive compound profiles. Microbiological analyses included total viable count (TVC), fungal count (TFC), and total lactic acid bacteria (TCLAB). Chemical analyses comprised polyphenol, flavonoid, anthocyanin, carotenoid, sugar, and vitamin C content, as well as antioxidant activity (DPPH, ABTS, reducing power). Thermal and structural stability were examined via thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Fermentation significantly increased the counts of lactic acid bacteria, achieving 8.38 and 7.86 log CFU/g after freeze-drying, respectively. While total polyphenols slightly decreased (by 9.5% and 1.1% for L. plantarum and F. fructivorans, respectively), flavonoid content increased notably by 16.1% in F. fructivorans-fermented samples. Antioxidant activities, assessed by ABTS and DPPH assays, were largely maintained, although a reduction in reducing power was observed. Additionally, fermentation led to sucrose hydrolysis, resulting in higher glucose and fructose contents, and increased water content in the final products. Minor increases in total fungal counts were noted after freeze-drying but remained within acceptable limits. Overall, the combination of fermentation and freeze-drying processes preserved key antioxidant properties, enhanced microbial safety, and produced functional peach-based products with improved bioactivity and extended shelf life. These findings highlight the potential of fermented freeze-dried peaches as innovative, health-oriented alternatives to traditional fruit snacks.

This study provides a comprehensive assessment of the effect of direct (probe) and indirect (bath) ultrasound treatments on the physicochemical and structural properties of red bell pepper (Capsicum annuum L.) tissue. Ultrasound was applied under controlled conditions to induce structural modification without excessive thermal or mechanical damage. The treated samples were evaluated using chemical (polyphenols, flavonoids, carotenoids, vitamin C, sugars), microbiological (total viable count (TVC) and total yeast and mold count (TYM)), spectroscopic (FTIR, NMR), thermal (TGA), and microscopic (SEM, micro-CT) analyses. Both ultrasound modes affected the tissue, but their effects differed in intensity and character. Direct ultrasound caused stronger cavitation and mechanical stress, resulting in greater cell wall disruption, higher permeability, and enhanced release of bioactive compounds such as polyphenols, vitamin C and antioxidants from the tissue matrix to the surroundings. Indirect ultrasound acted more gently, preserving cellular integrity and sugar profile while moderately increasing antioxidant activity. Cluster and correlation analyses confirmed that ultrasound mode was the main factor differentiating the samples. Short-term direct sonication enhanced the release of antioxidant compounds, whereas prolonged exposure led to their degradation, resulting in an overall decline in antioxidant capacity, and indirect ultrasound better preserved texture and sugar composition. This demonstrates that ultrasound mode and duration can be tailored to balance tissue integrity and enhance bioactive compounds in plant-based materials.

This study examined the influence of ultrasound pre-treatment and its parameters on the physical and chemical properties of bell peppers undergoing lactic acid fermentation. Two ultrasound methods were employed: immersion (for 15 and 30 min) and contact (for 1, 3, and 5 min). The fermentation process was carried out with the addition of Lactiplantibacillus plantarum ATTC 4080. The physicochemical and structural properties of both fresh and fermented bell peppers, including pre-treated and untreated samples, were analyzed, with untreated fresh and fermented peppers serving as control samples. The findings revealed that ultrasonic pre-treatment significantly affected the peppers’ physical, chemical, and structural characteristics. Specifically, ultrasound reduced dry matter content, with fresh bell peppers exhibiting the highest dry matter content (10.58%). Dry matter content decreased by 16–24% after ultrasound pre-treatment and by 0–14% after fermentation. The immersion method and longer sonication times had the most pronounced effects on dry matter reduction. In addition, ultrasound caused changes in color and texture, while fermentation influenced attributes such as hardness, elasticity, cohesiveness, and chewiness. The most significant changes occurred with 30 min of ultrasound treatment, leading to a 25.6% increase in red color, whereas the contact method increased yellow color, with a 30.3% increase between 15 and 30 min of immersion sonication. Fermentation generally reduced the proportion of red and yellow color compared to fresh samples, except for samples treated with contact ultrasound for 5 min, which retained higher red and yellow coloration after fermentation. Fermentation significantly softened the peppers, reducing hardness by up to 85% compared to fresh untreated samples. Chewiness followed a similar trend, decreasing from 17% to 80% in pre-treated samples and up to 90.65% after fermentation. Elasticity and cohesiveness also decreased with increasing sonication time and fermentation, but not significantly. Ultrasound pre-treatment had no significant effect on total polyphenol and carotenoid contents in fresh samples, which ranged from 43.55 mg β-carotene/100 g dry matter to 147.89 mg β-carotene/100 g dry matter. However, fermentation significantly increased carotenoid levels, with a 40% increase observed in samples treated with 5 min of contact ultrasound. In addition, pre-treatment methods helped to preserve polyphenols in fermented peppers. Levels of lactic acid bacteria (LAB) in fermented samples varied according to pre-treatment, with the highest LAB levels found in peppers exposed to immersion ultrasound for 30 min (10.55 log CFU/g). Despite ultrasound-induced tissue damage, fermentation proceeded effectively, resulting in consistent pH levels (ranging from 3.01 to 3.06) across all samples. Structural analysis showed that tissue damage increased with longer sonication times. In conclusion, ultrasonic pre-treatment significantly affected the physicochemical, structural, and bioactive properties of sweet peppers. While it reduced dry matter content and altered texture and color, it also helped to preserve polyphenols in fermented samples and increased carotenoid content after fermentation. The immersion method and longer sonication times had the most pronounced effects, highlighting ultrasound as a promising tool for modifying the properties of fermented vegetables.

Pulsed electric field (PEF) pre-treatment (1.07 kV/cm, 1, 5.5, 10 kJ/kg) was combined with lactic fermentation using Lactiplantibacillus plantarum to modulate red bell pepper matrix structure and subsequent in vitro bioaccessibility of bioactive compounds. Although PEF-assisted fermentation has gained increasing attention, its influence on post-digestion recovery of carotenoids and phenolics remains insufficiently characterized. Fermentation day 5 was identified as the, most favorable processing stage for preserving antioxidant capacity and bioactive compound stability. Moderate PEF (5.5 kJ/kg) enhanced carotenoid accumulation (>220 mg/100 g d.m.) and induced structural reorganization, confirmed by FTIR analysis. Following INFOGEST digestion, samples treated at 5.5 kJ/kg exhibited the highest apparent intestinal bioaccessibility (∼78% polyphenols; ∼39% carotenoids), whereas higher energy input (10 kJ/kg) reduced carotenoid recovery (∼22-24%), demonstrating a non-linear, energy-dependent response. Fermentation after moderate PEF shifted the relative amino acid profile toward a pattern closer to the reference protein, as reflected by higher EAAI values (1.26-1.36 vs 0.84 in the control), despite the decrease in total protein content and total essential amino acid content. These findings reveal intensity-dependent modulation of apparent bioactive release during digestion and provide mechanistic insight into structure-function interactions in fermented vegetable matrices.